/Engine/Source/Runtime/Engine/Public/ViewportClient.h
Check an axis movement received by the viewport. If the viewport client uses the movement, it should return true to consume it.
True to consume the axis movement, false to pass it on.
virtual bool InputAxis ( [FViewport](API\Runtime\Engine\FViewport) * Viewport, [FInputDeviceId](API\Runtime\Core\Misc\FInputDeviceId) InputDevice, [FKey](API\Runtime\InputCore\FKey) Key, float Delta, float DeltaTime, int32 NumSamples, bool bGamepad )